http://www.legitreviews.com/article/593/1/
AMD Has R680 Running Stable in CrossFire
these are the current 3870s. SINGLE GPU, that card is the one that is performance wise weaker then the 8800 gt by around 4-7 fps average in most games.. what most of you havent seen (not 100% sure if everyone here knows..) is that there is a DUAL GPU version called the 3890 (unoffcial) or some people call it the 3870 X2,
this picture shows 4 3870s (single gpu version) on a motherboard with 4 pci-e slots enabling quad crossfire.
THIS however is the dual GPU version, since it uses a DUAL SLOT cooling solution
only 2 video cards can fit, BUT rumours are in a company is planning on making a motherboard that can enable 4 of these monsters in Crossfire

that is the DUAL GPU version, notice the mounting brackets where the GPUs are located, and the memory chips beside them.
the X2 IS THE 8800 killer